In addition to general industrial use, such as large-sized critical rotating equipment like turbines or blowers, or rapid rotating equipment or critical equipment like compressors, the slide bearing is also used as a bearing of a diesel engine for a ship or a power generation facility. The slide bearing, in general, is not subjected to damage since it is surrounded by an oil film and rotates in a contactless manner. However, an execution failure or a blade unbalance can cause a coupling misalignment, and a rotating shaft can contact (rub) the slide bearing due to an abnormal vibration caused by an oil whip, thereby causing damage. When some kind of abnormality occurs in the slide bearing, a vibration or sound occurs that is different from usual. If an actuation is continued in such a state, damage may be caused. Moreover, if the rubbing abnormality continues, a burn may occur, thereby resulting in a stop in the equipment.
As a technique of diagnosing the slide bearing in order to avoid such situation, conventionally, a method using a shaft vibration due to an eddy current type sensor or a bearing housing vibration due to a piezoelectric acceleration sensor is suggested. For example, when a spectral pattern obtained by applying a fast Fourier transform (FFT) to waveform data such as vibrations or sound which occur from the slide bearing is compared to a preset spectral pattern in an emergency condition, the slide bearing could be diagnosed based on the compared result.
As a method for determining whether or not there is a rubbing in the slide bearing, etc. (contact between the rotational part and the stationary part), the following method is proposed, the method comprising: for example, detecting the sound which occurs when the rotating shaft contacts the bearing; retrieving the acoustic signal; subjecting the acoustic signal to an envelope detection process (envelope process); forming data after the envelope detection; comparing a cepstrum value with a reference value; and, based on this determination result, performing a rubbing determination (see patent document 1). If the occurrence of the rubbing phenomenon which is an initial stage of a burn damage of the slide bearing can be detected early, at a minor stage, the burn damage may be obviated.